\[\boxed{\mathbf{71}\mathbf{.}}\]
\[f(x) = (x + a)^{m};\ \ m \in N;\ \]
\[\ m > n;\]
\[f^{'}(x) = m(x + a)^{m - 1};\]
\[f^{''}(x) = m(m - 1)(x + a)^{m - 2}.\]
\[m(m - 1)(m - 2) \cdot \ldots \cdot (m - n) =\]
\[= \frac{m(m - 1)(m - 2) \cdot \ldots \cdot 1}{n(n - 1)(n - 2) \cdot \ldots \cdot 1}:\]
\[f^{(n)}(x) = m(m - 1) \cdot \ldots \cdot\]
\[\cdot (m - n)(x + a)^{m - n} =\]
\[= \frac{m!(x + a)^{m - n}}{n!}.\]